This invention relates to a scrubber for the cleaning of dust-loaded gas or steam. The scrubber may be of the type, in which the gas or steam is introduced downwardly into the scrubber through an inlet and washed with a washing liquid, for example water, in that the liquid is finely distributed over the flow path of the gas by means of suitably positioned nozzles. The washing liquid, which is collected on the scrubber bottom and includes dust washed out from the gas and possibly also other substances, is removed e.g. via a drain pipe.
The aforesaid scrubber type is utilized especially, among others, in the cellulose industry, for example at paper making, where it is applied in various vapour escapes and chimneys, for example in recovery boilers, mixing departments and clarifiers. This scrubber, however, is not sufficient for use under very difficult conditions. In a sulphate mixing tank for thick liquor for charging a recovery boiler, for example, raw sulphate is added together with sulphate ashes recovered from the recovery boiler and electrostatic precipitators, which are mixed together by means of stirrers. The thick liquor in the mixing tank has a temperature of about 108.degree. C., which gives rise to violent gas and steam formation in the tank, which are discharged via a vapour escape to the atmosphere. The emissions from the tank must be treated efficiently, in order to recover the heat in the waste gases and also to separate from the gases dust and substances to be recycled in the process. The violent gas and steam development which includes a large quantity of dust implies, that the known scrubber, in spite of intense pouring of washing liquid on its inside, is covered with emission products, particularly in the lower part of the scrubber. Also the inlet of the vapour escape in the scrubber is covered with solid substances included in the gas and steam. This layer of solids increases rapidly in thickness when the scrubber is in operation.
The present invention eliminates the shortcomings of known heat recovery and condensate systems and renders it possible, by the scrubber according to the invention to efficiently clean and recover heat from a gas and/or steam mixture heavily contaminated by dust while the scrubber is continuously in operation.